> If you asked a random person what Columbus discovered, what would they answer? Round here I think most people would say that Columbus discovered America. By landing in San Salvador and then Cuba.

Do they actually know where he landed? I think that other than your Columbus example it would be very rare for people to say "America" to mean either or both continents.

Most people I know would say America for the US, North America, South America, or the Americas as appropriate. when referring to the continents.

Other than The Economist's usage, "The Americas" is used by other publications and books, its the name of a TV series, its the title of most wikipedia articles relating to the two continents.

It appears to be "open to uncertainties" but is the commoner usage: https://en.wikipedia.org/wiki/Americas#cite_note-oxfordc-3